This invention relates to air driven centrifuges and more particularly is directed to means incorporated within the rotor seat of the centrifuge to increase the dampening of any excessive vibration or fluttering of the rotor during certain critical speeds of rotation.
It has been determined in the past that air driven centrifuges provide significant advantages in producing ultra high speed centrifugation. Certain fluid mixtures require extremely high rotational speeds for separation. One example of such a requirement is with respect to the separation of materials in blood such as protein which require extremely high speeds. Other processes which require these very high speeds of rotation are the separation of minute viruses such as rubella, the concentration of viruses from clinical specimens, the concentration of immunoglobulins from urine, saliva and bronchial washings, and quantitative electron microscopy such as particle coating.
In addition, air driven centrifuges provide unique advantages in that there are no bearings requiring lubrication, since the rotor rides on a cushion of air. Since there are no contacting parts with respect to rotation of the rotor, there is no wearing of mechanical parts. It has been found that there is extreme stability at high speeds and that these high speeds can be obtained without accompanying excessive heat.
Since it is impossible to mechanically construct a rotor and its associated components in a centrifuge with such precise accuracy that it would be one hundred percent in balance, a certain amount of imbalance may be caused by slight imperfections in the rotor that may exist either in the threads or flutes on the rotor, for example, or possibly in the orientation or operation of the air jets. Consequently, during certain critical rotating speeds these imperfections may accumulate to the point that the rotor may be subjected to excessive vibration or wobbling which could cause the rotor to become dislodged from its rotor seat and thrash around within the centrifuge.
Prior art approaches have been developed for helping to attenuate the problem of any deliterious vibration. One example is the Hein U.S. Pat. No. 3,456,875 which shows the use of a stationary stator having a floating stator pad mounted thereon with a plurality of feet or buttons located on the bottom of the stator pad. During normal operations this floating stator pad provides an ability to alleviate nearly all problems with respect to excessive vibration.
However, it has been determined in practice that the operation of the floating stator pad has not been completely satisfactory, since the rotational operation of the centrifuge has not been as stable and as smooth as desired. In some instances imperfections or other contributing factors in the rotor design or operation may combine to cause the rotor to become dislodged and crash within the centrifuge.
Therefore, it is necessary to provide some type of means for making the stator pad operate more efficiently to create a better dampening of the rotor during its operation to provide the necessary smooth and stable operation which is critical to the successful use of an air driven centrifuge. Otherwise, not only is there a possibility of the rotor thrashing around within the centrifuge and causing damage to the rotor and/or centrifuge, but also the centrifugated constituents of the sample in the rotor will become remixed and ruin the centrifugation run.